Being the first active circuit after the antenna, the low-noise amplifier (LNA) is a critical building block for radio transceivers at millimeter-wave frequencies. To increase receiver sensitivity and reduce the amount of noise contributed by subsequent states, the LNA is required to have a moderate gain and a low noise figure. Also, the LNA should be unconditionally stable (i.e., not oscillate when attached to other components), and impedance matched to its surrounding environment.
Typically, millimeter-wave LNAs are built in III-V technologies as individual chips, see, e.g., L. Tran et al., “High Performance, High Yield Millimeter-Wave MMIC LNAs Using InP HEMTs,” IEEE IMS Digest, p. 9-12, June 1996; M. Siddiqui et al., “GaAs components for 60 GHz wireless communication applications,” GaAs Mantech Conference, April 2002; A. Fujihara et al., “High performance 60-GHz coplanar MMIC LNA using InP heterojunction FETs with AlAs/InAs superlattice layer,” IEEE IMS Digest, p. 21-24, June 2000; K. Nishikawa et al. “Compact LNA and VCO 3-D MMICs using commercial GaAs PHEMT technology for V-band single-chip TRX MMIC,” IEEE IMS Digest, p. 1717-1720, June 2002; and K. Onodera et al., “V-band monolithic low-noise amplifiers using ion-implanted n+-self-aligned GaAs MESFETs,” IEEE Microwave Guided Wave Ltr., v. 9, n. 4, p. 148-150, April 1999, the disclosures of which are incorporated by reference herein. These LNA chips are then packaged, often with waveguide connectors. Realizing a full millimeter-wave transceiver involves assembling multiple chips, often with these bulky waveguide connectors, into a fairly large and expensive solution.